University of North Carolina at Chapel Hill Graduate School
Doi
Abstract
Global climate change has rapidly altered marine systems, resulting in negative impacts on tropical reef-building corals around the globe. As the leading driver of coral bleaching, ocean warming disrupts the mutualistic relationship between reef-building corals and their algal symbionts (Symbiodinaceae) in a process known as coral bleaching. During periods of elevated sea temperatures corals expel their symbionts causing declines in metabolic and physiological function. Mass bleaching events deteriorate coral reefs, reducing the ecosystem services they provide including foundational habitat which host 32 of 34 recognized marine phyla of the ocean’s biodiversity, impacts on reef fisheries, physically protecting coasts from storms by reducing erosion, and elevates economic income of coastal communities. To reduce the impacts of warming, conservationists are attempting to protect and revitalize these systems by identifying resilient reefs. The goal is then to enhance coral abundance and preserve coral genetic variation with coral farming, and related restoration efforts. These activities are relatively new and identifying resilient corals and refining coral restoration techniques are only just beginning. Identifying how different coral species respond to restoration activities and their responses to temperature in general is critical in understanding coral persistence in the future. This dissertation examines the effect temperature has on coral survival, metabolism, and physiology from three conservation perspectives to enhance restoration methodologies in Caribbean and north Atlantic coral ecosystems. In Chapter 1, I identified a potential thermal refuge habitat in Bermuda by comparing thermal tolerance, optima, and sensitivities of four coral species from shallow and upper-mesophotic reef habitats. In Chapter 2, I used metabolic thermal performance curves (respiration and gross photosynthesis) to assess the effectiveness of stress-mediating interventions to alter thermal performance during heat stress, for use in coral farming. The results from this work highlight how variation in genotypes can influence metabolic and physiological responses (Acropora cervicornis) to thermal stress. In Chapter 3, I showed how genotypic variation (Orbicella annularis) and environmental interactions are necessary in planning and understanding the success of coral restoration across environmental gradients. Overall, investigating how corals respond to temperature stress and restoration methodologies are important in predicting the future persistence of corals and identifying successful procedures to enhance coral conservation.Doctor of Philosoph
